Thrombosis of artificial graft surfaces in small caliber vessels is a major problem in both cardiac and peripheral vascular surgery. Synthetic vascular grafts are inherently thrombogenic and, when prosthetic material is used to bypass medium-sized or small arteries, thrombotic obstruction is a major problem. Although the systemic administration of plateletaggregation inhibitory or anticoagulant drugs has been generally successful, considerable difficulties and the disadvantages of side effects have been experienced. See, P. Gloviczki, et al., "Prevention of Platelet Deposition by Ibuprofen and Calcium Dobesilate in Exapanded Polytetrafluoroethylene Vascular Grafts," AM J Surg 1985;150:589-592. The contents of this and each of the other documents and articles mentioned herein are hereby incorporated by reference in heir entireties. See also Laurence A. Harker et al, "Pharmacology of Platelet Inhibitors," JACC Vol. 8, No. 6, Dec. 1986:21B-32B. Also, endothelial seeding of graft surfaces to reduce blood clotting is a tedious and expensive procedure. See, e.g., J. C. Stanley et al., "Enhanced Patency of Small-Diameter, Externally Supported Dacron Ibofemoral Grafts Seeded with Endothelial Cells," Surgery, Vol. 92, No. 6, pp 994-1005, Dec., 1982. Further problems encountered with artificial organs are discussed in H. E. Kambic, et al., "Biomaterials in Artificial Organs," C & EN, 4/14/86. Accordingly a need has arisen for an improved method for reducing the incidence of thrombosis resulting from surgical implants which method is simple, relatively inexpensive, and does not have side effects and problems experienced with the prior methods.